Two stage torque control method for a vehicle transmission

Abstract

A semi-automated vehicle transmission includes a method of returning torque control to the driver of the vehicle. The transition from an initial current torque value to a desired torque value is accomplished in two stages. A first rate of change is utilized during a preselected time period or until the current torque value corresponds to the desired torque value. In the event that the desired torque value is not achieved during the preselected period of time, then a second rate of change is implemented. The second rate of change preferably is very aggressive relative to the first rate of change. The rate of change of the current torque value is accomplished within a window of available torque limits that progressively change with time.

We claim:  
     
       1. A method of controlling a current torque value in a vehicle transmission, comprising the steps of: 
       (A) determining a desired torque value for use during a portion of a shifting operation;  
       (B) defining a condition when the current torque value corresponds to the desired torque value;  
       (C) changing the current torque value at a first rate of change so that the current torque value approaches the desired value from step (A) until the condition from step (B) exists or a preselected period of time lapses;  
       (D) determining whether the condition from step (B) exists when the preselected period of time elapses; and  
       (E) when the condition from step (B) does not exist when the preselected period of time elapses, changing the current torque value at a second rate of change that is greater than the first rate of change until the condition from step (B) exists.  
     
     
       2. The method of claim  1 , wherein step (A) is performed by approximating the desired torque value by determining a driver requested torque value that corresponds to a driver requested gear ratio. 
     
     
       3. The method of claim  1 , wherein step (C) is performed by setting a torque limit, changing the current torque value to be within the set limit, and changing the limit at the first rate as a function of time such that the current torque value changes at the first rate. 
     
     
       4. The method of claim  3 , wherein step (C) is performed by progressively increasing the limit. 
     
     
       5. The method of claim  3 , wherein the torque limit has a maximum and a minimum value and wherein step (C) is performed by progressively changing the maximum value until the maximum value corresponds to the desired torque value and progressively changing the minimum value until the minimum value corresponds to a predetermined absolute minimum value. 
     
     
       6. The method of claim  5 , wherein step (E) is performed by setting a torque limit, changing the current torque value to be within the set limit, and changing the limit at the second rate as a function of time such that the current torque value changes at the second rate, and wherein the torque limit has a maximum and a minimum value and step (E) is performed by progressively changing the maximum value until the maximum value corresponds to the desired torque value and progressively changing the minimum value until the minimum value corresponds to a predetermined absolute minimum value. 
     
     
       7. The method of claim  3 , wherein step (C) is performed by changing the current torque value to correspond to the torque limit. 
     
     
       8. The method of claim  1 , wherein when the desired torque value is less than the current torque value, step (C) is performed by progressively decreasing the current torque value at the first rate. 
     
     
       9. The method of claim  1 , wherein when the desired torque value is greater than the current torque value, step (C) is performed by progressively increasing the current torque value at the first rate. 
     
     
       10. The method of claim  1 , wherein step (E) is performed by setting a torque limit, changing the current torque value to be within the set limit, and changing the limit at the second rate as a function of time such that the current torque value changes at the second rate. 
     
     
       11. The method of claim  10 , wherein step (E) is performed by progressively increasing the limit. 
     
     
       12. The method of claim  10 , wherein the torque limit has a maximum and a minimum value and wherein step (E) is performed by progressively changing the maximum value until the maximum value corresponds to the desired torque value and progressively changing the minimum value until the minimum value corresponds to a predetermined absolute minimum value. 
     
     
       13. A method of controlling a current torque value in a vehicle transmission, comprising the steps of: 
       (A) determining a desired torque value;  
       (B) defining a condition when the current torque value corresponds to the desired torque value;  
       (C) setting a torque limit having a maximum and a minimum value;  
       (D) changing the current torque value so that the current torque value is within the limit from step (C) and the current torque value approaches the desired value from step (A);  
       (E) progressively changing the torque limit so that the maximum limit value approaches the desired torque value and the minimum limit value approaches a preselected absolute minimum value;  
       (F) reperforming steps (D) and (E) until the condition from step (B) exists.  
     
     
       14. The method of claim  13 , wherein steps (D) and (E) are performed by changing the torque limit at a first rate for a preselected amount of time and then changing the torque limit at a second rate that is greater than the first rate after the preselected amount of time has elapsed. 
     
     
       15. The method of claim  14 , wherein step (D) is performed by changing the current torque value to correspond to the torque limit such that the current torque value approaches the desired torque value. 
     
     
       16. The method of claim  13 , wherein step (F) includes the substep of determining whether the condition from step (B) exists. 
     
     
       17. A method of controlling a current torque value in a vehicle transmission, comprising the steps of: 
       (A) determining a desired torque value for use during a portion of a shifting operation;  
       (B) changing the current torque value to a value within an available torque window such that the current torque value approaches the desired torque value;  
       (C) progressively expanding the available torque window at a first rate of change until the current torque value corresponds to the desired torque value or a preselected period of time elapses;  
       (D) when the current torque value does not correspond to the desired torque value and the preselected period of time has lapsed, progressively expanding the torque window at a second rate of change until the current torque value corresponds to the desired torque value.  
     
     
       18. The method of claim  17 , wherein the second rate of change is greater than the first rate. 
     
     
       19. The method of claim  18 , wherein the desired torque value is greater than the current torque value and wherein step (B) is performed by changing the current torque value to correspond to a maximum value within the available torque window such that the current torque value approaches the desired torque value at a rate equal to the rate that the available torque window expands.